1. Field of the Invention
This invention relates to a projection apparatus for enlarging and projecting images on a personal computer and images on TV, movies or the like onto a screen or the like, and particularly to a projection apparatus adapted to enable a central portion of a projected image to become brighter to emphasize information of characters, images or the like displayed on the central portion of the screen.
2. Related Background Art
Referring to FIG. 12 of the accompanying drawings which shows the optical system of an image projection apparatus according to the prior art, the reference numeral 1 designates a light source such as a discharge lamp, and the reference numeral 2 denotes a parabolic mirror. The reference numeral 3 designates an optical integrator comprising lens arrays 31 and 32. Also, the reference numeral 4 denotes a polarization converting element array for converting non-polarized light into polarized light having a particular polarization direction, and multiple elements each comprising a polarization separating surface 41, a reflecting surface 42 and a half wavelength plate 43 are arranged.
The reference numeral 5 designates a condensing lens, the reference characters 6R, 6G and 6B denote image display elements for displaying images of respective colors R (red), G (green) and B (blue), and the reference numerals 7 and 8 designate dichroic mirrors constituting a color separating system.
The reference numeral 9 denotes a relay system for directing the illuminating light of B to the image display element, and the relay system 9 comprises relay lenses 91 and 92 and mirrors 93 and 94.
The reference numerals 10 and 11 designate mirrors, the reference characters 12R, 12G and 12B denote condenser lenses for guiding illuminating light to a projection lens, the reference numeral 13 designates a color combining prism for combining R, G and B lights into one, and the reference numeral 14 denotes a projection lens.
The integrator 3 is used to uniformly illuminate the image display elements 6R, 6G and 6B. The action of the integrator 3 will now be described with reference to FIG. 13 of the accompanying drawings. In FIG. 13, the polarization converting element array 4 and the dichroic mirrors 7, 8 are omitted to describe the action of the lens arrays 31 and 32 of the integrator 3.
An illuminating beam Q from the parabolic mirror 2 is divided into a plurality of beams qi by the lens array 31 and the beams qi are condensed near the lens array 32. When at that time, the shape of the aperture of each lens constituting the lens array 31 is made into a rectangle similar to the shape of the image display element 12, each beam is condensed (diverges) as a beam of a rectangular cross-sectional shape. These beams have their direction changed into a predetermined direction by the condensing lens 5, and are gathered so as to overlap one another on the image display element 12. The unevenness of the intensity of the beam Q on the lens array 31 becomes small by the beam Q being divided into a plurality of beams and the plurality of beams being added up, and the uniformization of illumination has been realized.
As described above, the uniformization of the intensity distribution on the image display element 12 becomes possible by the integrator 3, but on the other hand, when data prepared by a personal computer is to be displayed by the use of the image projection apparatus, characters or an image is displayed on a central portion of the screen. Therefore, to emphasize information, it is desired that the central portion on which the information is present be set more brightly. So, methods of making the central portion of the screen brighter than the peripheral portion thereof are disclosed in Japanese Patent Application Laid-Open No. 9-54279 and Japanese Patent Application Laid-Open No. 9-159968. The method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 9-54279 is designed to shift an illuminated area by each lens toward periphery and illuminate it by the use of a lens array set so as to illuminate a portion narrower than an effective area to thereby change the intensity of the central portion and the peripheral portion. Such a construction, however, suffers from the problem that much of the illuminating light illuminating the peripheral portion illuminates the outside of the effective range of the image display element and this is a great loss of the quantity of illuminating light.
Also, the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 9-159968 is to make the central lens of a fly-eye lens larger than the other lenses thereof, and set the size of the large central lens so that the peripheral illuminance of a projected display image may be about 50% of the central illuminance thereof. In this construction, the effective area of the image display element is illuminated with a uniform size by individual lenses constituting a lens array, and the central portion is made brighter than the peripheral portion by the unevenness of intensity created in the lens of the central portion of which the size is set large. Such a method, however, suffers from the problem that a dark portion by a hole in a reflecting mirror created in the central portion of a beam emitted from the reflecting mirror is created at the center of the screen and therefore the image becomes an unnatural and very unsightly image.
The present invention has as its object to provide a projection apparatus which can solve or mitigate the above-noted problems peculiar to the prior art. Here is disclosed a projection apparatus which can make the central portion of a projected image brighter without the loss of the quantity of light to naturally emphasize information such as characters or an image displayed on the central portion of a screen or the like.
The projection apparatus of the present invention is a projection apparatus in which an optical integrator is illuminated with light from a light source, one or more image display elements is irradiated with a plurality of beams from the optical integrator, and image light from the image display element or elements is projected by a projection optical system, wherein the illuminating range of some of the plurality of beams is made smaller than the illuminating range of the other beams.
Also, the projection apparatus of the present invention is a projection apparatus in which an optical integrator provided with a lens array is illuminated with light from a light source, one or more image display elements is irradiated with a plurality of beams from the integrator, and image light from the image display element or elements is projected by a projection optical system, wherein the optical integrator is designed such that some of the plurality of beams illuminate substantially only the central portion of the image display element or elements and the other beams illuminate the central portion and the peripheral portion of the image display element or elements.
In the above-described projection apparatus, the optical integrator is provided with at least two lens arrays, and when the size of the individual lenses of the lens array on the light source side is defined as p and the focal length of the individual lenses of the lens array on the image display element side is defined as ff2 and K defined by
K=p/ff2
is K value, the integrator is comprised of a combination of lenses differing in K value from each other.
In the above-described projection apparatus, in the K value, the ratio between the maximum value Kmax and the minimum value Kmin of the K value satisfies
xe2x80x831.2 less than Kmax/Kmin less than 2.
In the above-described projection apparatus, the lenses differing in the K value are comprised of a combination of lenses differing at multiple stages in the K value.
In the above-described projection apparatus, a polarization converting element array is provided on the light emergence side of the optical integrator, and the polarization converting element array is comprised of a combination of elements differing in the pitch of polarization separating surfaces and reflecting surfaces from one another.
In the above-described projection apparatus, the optical integrator is provided with at least two lens arrays, the focal lengths of a certain lens and other lenses of the lens array on the image display element side differ from each other, and the lens array on the light source side is disposed separately by a distance conforming to the different focal lengths.
In the above-described projection apparatus, the lens array on the light source side is disposed separately at multiple stages in conformity with the focal lengths of the lenses of the lens array on the image display element side.
In the above-described projection apparatus, the optical integrator is provided with at least three lens arrays, the combination of the individual lenses of these lens arrays is changed by at least two lens arrays on the image display element side, and the combined focal lengths by the respective corresponding lenses of the lens arrays differ from each other.
In the above-described projection apparatus, the optical integrator is comprised of a combination of the lens arrays described in the thirdly described projection apparatus and the lens arrays described in the seventhly or eighthly described projection apparatus.